Is it just Puberty ?

[villain]

I think i may be underweight im 13 and around 70 to 80 pounds idk and is it because i have a fast metabolism is it because i dont eat much or is it just puberty?

[StoppingTime]

I think it is mostly because you have a fast metabolism, and also because of family heredity. I am similar in weight to you as well and also 13, and it is normal for you.

[steve14]

i would kill to be that weight.

[Kujiro]

It is possible that puberty has caused a surge in your metabolism, but we cannot rule you that genetically you are already having a high metabolic rate.

Some people just cant put on much weight even if they eat a ton, while others just gain tonnes by eating a bun.

I believe you may have to focus on these 2 possibilites. Unless you do have pertaining medicial issues which causes this, else you are pretty good.

Cheers
*smile*

[JJIIYY312]

you should be eating enough each day if you have a problem though you should see a doctor

[Unlucky_Leprechaun]

Eat normal and healthy is the best advise I think. If you know that you are not eating enough then you may have a medical issue that you need to get looked at. Im not a big guy either, but I feel I eat fairly normal. I'm 5-6 122 and 17. This is what I found and it seems like fairly good advice:
Weight is depending upon height more so then age. At five feet tall a person is suppose to weigh about a 100 pounds for a healthy weight and anywhere from 5 to 8 pounds for every inch after that

Edited:
I may have not have ate as healthy (at times) as I should have, but I don't have bulimia or anorexia. I just never seem to get hungry. I have been doing a lot better now and do not fluctuate as much as I have. So my first part of this about eating normal and healthy may have been overstating exactly what I have done myself, sorry to have misled in any way.

[haslam1919]

probably fast metabolism , i was the same way when i was younger